Such auxiliary operating mechanisms are used in control cabinets, the operating mechanism of the switching device being non-rotatably connected to an externally operable door coupling rotary handle when the control cabinet door is closed. Opening the control cabinet door breaks the non-rotatable connection between the operating mechanism and the door coupling rotary handle. Typically, auxiliary operating mechanisms are provided to allow the operating mechanism of the switching device to be actuated even when maintenance work is being carried out on the switching device.
To ensure that when the control cabinet door is open, the switching device can be turned on deliberately and be turned off as quickly as possible, U.S. Pat. No. 7,071,527 B2 describes an auxiliary operating mechanism which is connected to an electromechanical switching device mounted in a control cabinet and which is in engagement with an externally operable door coupling rotary handle when the control cabinet door is closed. When opening the control cabinet door, the auxiliary operating mechanism moves out of engagement with the door coupling rotary handle. The auxiliary operating mechanism has a handle housing which is formed with grip elements is and mounted about an actuating shaft in such a way that it is rotatable and axially displaceable to a limited extent. The actuating shaft is connected to the operating mechanism of the switching device and is movable into engagement with the door coupling rotary handle as the control cabinet door is closed. The handle housing contains therein a polygonal ratchet wheel which is mounted on the actuating shaft in such a way that it is rotatable and axially displaceable to a limited extent and which, in conjunction with axially extending first ribs formed on the inner wall of the handle housing, forms a unidirectional rotary coupling. This unidirectional rotary coupling has the effect that when a single rotational movement is imparted to the rotary handle in only one of the two directions of rotation, this rotational movement will be transmitted to the actuating shaft, whereas in the other case, no transfer of movement will take place. Thus, an effect will be produced only by the switch operating movement imparted via the handle housing in one direction, preferably in the direction for turning the switching device off. The handle housing further contains therein a coupling wheel which is non-rotatably mounted on the actuating shaft in such a way that it is axially displaceable to a limited extent and which has axially extending second ribs formed on its periphery A helical spring is braced between the coupling wheel and the ratched wheel and acts upon the coupling wheel relative to the handle housing in a direction away from the switching device, the coupling wheel abuting a ring-shaped housing part which is formed with grip elements and is screwed to the handle housing at one end. In this condition, the rotational movement of the handle housing can only be transmitted via the unidirectional rotary coupling. When the door coupling handle comes into engagement as the control cabinet door is closed, or when pulling on the handle housing when the control cabinet door is open, the coupling wheel is displaced axially relative to the handle housing against the force of the helical spring, thereby moving the second ribs of the coupling wheel in between the first ribs in the handle housing. In this condition, motion is transferred from the handle housing to the actuating shaft in both directions of rotation. This bidirectional motion transfer now allows for switch operating movements in both directions, i.e., both for turning the switching device off and for turning it on. This auxiliary operating mechanism has the disadvantage that it is expensive and complex to manufacture.